| In the past 30 years, research on toxic pollutants mainly focuses on the industrial chemicals and pesticides, and the study on environment pollution of the Pharmaceuticals and Personal Care Products (PPCPs) only begins since 10 years. With the economic development and the life quality improvement, a lot of new PPCPs are used, and the compounds structure become more and more complicated, which makes it more difficult to be removed from water bodies.As a typical PPCPs, the iodinated contrast media (ICM) have unique chemical structures. They go through the human body without any metabolism, and are discharged into the urban sewage. ICM have biological inert and persistence, their removal rates from conventional water treatment technology are very small.additionally, their degradation rate by ozone is also limited. Thus, ICM have been classified as "the most dangerous pollutant". Therefore, it is important to carry out the theoretical research and practical engineering on the removal of ICM, and it is essential to find out the effective removal processes for ICM and study the removal mechanism and energy efficiency.In the paper, iopromide was selected as the model pollutant which is a typical ICM. Because of the low concentration of iopromide in the water environment, the analytical method based on solid phase extraction-high performance liquid chmatography has been established for the determination of iopromide in water. Some parmeters which may affect the recovery and chromatographic peak were investigated, and the method was tested in the actual water detection. The relationship between the input and the output voltage/current, and the performance of degradation by the double dielectric barrier discharge reaction kettle was investigated. The results indicated that:the relation between input power and average output peak power presents as a linear relationship, the linear equation was y=0.0595x-0.9379, correlation coefficient r=0.9892. The degradation experiment on acetic acid and tartrazine indicate that double-dielectric barrier discharge produced particles with oxidation activity, such as·OH, with a high efficiency. These active species played important roles in the degradation of organic polltants.The optimal removal condition of double dielectric barrier discharge reaction kettle was investigated. It was found that the removal rate of iopromide would increase with the increase of input power and reaction time, best conditions were:the input voltage 50V, the current 1.08A and the reaction time 10min. Under this condition, the removal rate could be as high as 100%, TOC removal rate was low, while B/C increased from 0.02 0.6 after treatment. The increase for concentration of NO3- was less than 7% of the theoretical one, the concentration ofⅠ- was 89.5% of the theoretical one. It was found that under the optimal reaction condition, the plasma channel produced presented more uniform distribution, and the energy input to the system was more efficiently used in breaking iopromide, while it failed to mineralize iopromide completely. This conclusions was proved by the biodegradability increase and the following biological treatment in SBR process. After the further biological treatment, the quality of effluent reached the level 1A emission standard of STP.Ozonation process and atomization plasma process were compared with double dielectric barrier discharge reaction kettle in treating the iopromide wastewater,at the same time, GAC adsorption technology, which was often used in the water supply process was compared also. The results showed that the ozone process and atomization plasma process had the iopromide removal rates of 32.8%,13.39% respectively, the biodegradability was improved to 0.3 and 0.13 respectively. But there were still some iopromide retained in liquid phase. In addition, the concentrations of freeⅠ- in the wastewater after treatment were low, that is to say that the iopromide still existed in the form of halide. The results of GAC experiment showed that:when the dosage was 5 g/L, the adsorption time was 192 h, the removal rate was still less than 50%, While the HRT of GAC filter stage in full-scale water supply process was only 3～4 h, and the dosage was far less than 5 g/L. The iopromide which could not be removed effectively would finally go into human's bodies, and bring potential harm to health. Comparing DBD reactor treatment process with ozone, atomization plasma process and activated carbon process for the treatment efficiency of iopromide, it was found that DBD technology was more applicable with a easier operation, simple process, shorter reaction time and better removal efficiency.From the results of HPLC, FIRT and UV etc under the best reaction conditions, it could be concluded that the DBD system generated active oxidate particles which attacked the bonds of C-I, C-N, and other unsaturated bonds. The degradation of iopromide by double dielectric barrier discharge technology was pseudo-first-order reaction, the degradation dynamic equation was C= C0×e-0.1349t.The energy utilization rate of DBD process and atomization plasma process were 1.52×10-10mol/J and 6.43×10-10mol/J respectively.the electric energy utilization rate of the two processes above and the ozone technology respectively were 0.42×10-8mol/J,1.43×10-8mol/J and 1.92×10-8mol/J respectively. But when the increase of biodegradability was considered into the consumption ratio, the energy utilization rate and electric energy utilization rate of DBD process were 6.6×10-7/J and 3.1×10-5/J respectively. The energy utilization rate of atomization plasma process was 9.7×10-9/J, the electric energy utilization rate of ozone technology was 5.6×10-7/J. If only the removal of iopromide molecule,was considered, the utilization rate of energy and electric energy of DBD process were lower than those of atomization plasma technology and ozone process, but when the biodegradability was considered, the utilization rate of energy and electric energy of DBD process were higher than those of atomization plasma technology and ozone process. |
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